Spark-plug.



SPARK PLUG.

APPLICATION FILED IuLY I2, 1915.

Patent-ed Sept. 26, 1916.

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FREDERICK 1li'. FURBER, 0F REVERE, MASSACHUSETTS.

Speccaton of Letters Patent.

Patented Sept., 26, 1916i.

Application filed July l2, 1915. Serial No. 39,337.

To @ZZ Iwhom it may concern:

Be it known that l, FREDERICK M. FUR- Bnn, a citizen of the United States, residing at Revere, in the county of Suffolk and State of Massachusetts, have invented certain lmprovements in Spark-Plugs, of which the following description, in connection with the accompanying drawings, is a speciiication, like reference characters on the drawings indicating like parts in the several figures.

rlhis invention relates -to spark plugs lof the character commonly used in internal combustion engines and has particular reference to a spark plu@r of the general type shown in my prior` atent No. 1,126,974, granted February 2, 1915.4 rlhe spark plug shown in thispatent comprises an outer shell or body provided with a gradually tapered bore and aninsulator which is secured in sa'idbody by a soft, metal bushing that engages frictionally the outer surface of the insulator and the wall of said bore and is shaped to compensate for the variations in shape between the insulator and the bore. According to the preferred method of making this plug the bushing is forced on to the insulator, thus causing it to conform to the surface of the insulator, and the outer surface of the bushing is then turned down to fit the seat formed for it in the bore of the body. This construction has proved exceedingly satisfactory and because of its extreme simplicity can be manufactured very The present invention aims to improve the construction shown in the patent above designated witha view particularly to effecting a further economy in manufacture.

The invention will be readily understood from the following description, reference being made to the accompanying dra-wings, in wliicli l Figure l is a vertical, sectional view through a spark plug showing one step in the processof manufacture; Fig. 2 is a view similar to Fig. l, showing a further step in the process of manufacture; Fig. 8 is a vertical sectional view through a completed spark plug constructed in accordance with this invention; and Fig. 4 is a view in side elevation of the plug` shown in Fig. 3.

Referring now to the drawings, 2 indicates the shell oi body of the plug which preferably is niade from bar'stock jof hexagonal cross section by turning oft to the body is then drilled and reained to forni a bore 6 which preferably is made cylindrical in shape from the lower orinner end of the body (referring to its normal position) to a point slightly above the reduced portion and is then tapered gradually from this point to the outer end of the body. This taper preferably is made very gradual and is of the character sometimes termed a sticking taper. rl`his body is substantially like that shown inthe patent above designated.

The insulator 8 niay be constructed sub stantially like that shown in the patent above referred to but preferably is provided just bclaw its middle with an enlargement 9, thus providing a shoulder 10 at the lower end of said enlargement and a shoulder 1l above it. The portion of the insulator above the part 9 preferably is tapered to conform to the tapered bore of the body 2. A series of gaskets 12 encircle the tapered part of the insulator and are fitted so tightly in -the tapered portion of the boreof the body that their frictional engagement between the body and insulator holds the insulator sediameter than either the outer end of the bore 6 or the tapered part of the insulator adjacent to the enlargement 9. Conscquently they will tend to hold the insulator in substantially the position in the bodyin which it is indicated in Fig. l. rThe plug is now placed in a die 14 having a holel fornied therethrough to receive the upper end of the insulator, this hole being of a diameter slightly smaller than that of the outerend'of the bore G. Another gasket 15, like the gaskets 12, is placed on the end of the insulator below the shoulder 1G. While the plug is supported in an inverted position in the die le, as shown in Fig. 2, a holbore into substantially the positions shown in Figs. 2 and 3. During this movement the upper shoulder 11 on the insulator engages the lowermost gasket' 12 and transmits to the series of gaskets the longitudinal movement of the plunger, whilethe-movement' of the lirger portion of the taperedl part of the insulator` into a smaller part of the tapered portion of the bore compresses the gaskets laterally and lattens them out, forcing them-to completely fill the space between the insulator and the body and to conform to the differences in shape between l the tapered surfaces of the insulator and bore. rIhe die 14 prevents the forcingof the gaskets out of the'bore of the body although obviously the upper end of the body could be provided with an inturned lip or ange that would perform this function. Since these gaskets are made of a soft metal and have a yielding core they Conform readily to the differences in shape between the surface of the insulator and the tapered wall of the bore. Suicient pressure is used on thel plunger 16 to force the insulator and gaskets into the body so. rmly that the insulator cannot be unseated without employing pressures exerted inwardly on the p the end of the plunger 16.

It is obvious that this construction avoids the necessity for the machine work required in the manufacture of the plug of my prior patent to fit the insulator bushing to its seat in the body. It also avoids one of the pressing operations, namely, that required to force the bushing on to the insulator.

The construction provided by this invention is of further advantage in producing a tighter joint between the insulator and body` than could be obtained in the construction shown in the patent. The tapered surfaces of -the insulatorsare so irregular that it is not always possible to produce a tight joint between the bushing and the insulator itself. In the present construction, however, the gaskets 12 each conforms independently of lthe yothers to the cross sectionalarea of the annular space in which they are confined between the'insulator and bore. Theshape of this space varies at successive pointsalong the insulator 'due chiefly to the' warping of' the insulator in its process of manufacture ideata@ than would be possible -with a single piece.

of soft-metal of even armuch greater length than the length of the entire series of-gaskets and it produces a joint between the insulator and body that is tight even after llong use and at very high temperatures.

If desireda short sleeve 18, preferably made of steel or of the material from which the body l is made, can be forced into the cylindrical part of the bore 6as shown in Fig. 3, until it bears against the gasket 15 whereit will serve as an additional means for resisting the backward movement of the insulator. When this member is to be used it should be made very slightly larger in diameter than the diameter of the bore; its upper edge should be beveled on the outside; and it should then be forced into the bore by the plunger 16. Ordinarily this sleeve will not be necessary but it can be used where a particularly substantial construction 'is desired.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is z- 1. In a spark plug, a. body having a bore gradually tapered toward one end, an insulator positioned in said bore and having a part tapered in the same direction as said bore, and a plurality of gaskets encircling the tapered part of said insulator and seated in the tapered portion of said bore, said gas- 'kets operating through their frictional engagement with said insulator and said body as the sole means for holding the insulator in the body.

2. In a spark plug, a body having a bore gradually tapered toward one end, an insulator positioned in said bore and having a part tapered in the same direction as said bore, and a plurality ofmetallic gaskets interposed between the tapered part of said insulator and the tapered portion of said bore and operating. through their fric'tionalv engagement with said insulator and bodv to hold the insulator in the body. 4

3. In a spark plug, a body having a bore formed therethrough, said bore having a portion gradually tapered toward the outer end of the body, an insulator positioned in said bore and having a part tapered to cor# respond to the taper of said bore and having an enlargedA portion below said taper, 'a plurality of gaskets independent of each other encircling' the tapered part of said insulator and llin(T the space above said enlargement between the tapered surface of the insulator and the tapered bore of the body, said in* sulator being supported in'said body solely This by the trictional engagement ont said gaskets with the insulator and the bore of the body.

iin a spar r plug, a bedy having a bore gradually tapered toward its outer end, an insulator position bore, a pluralityer?` gaskets independent oi l each other enclreling the tapered part of said insulator end-seated inthe tapered portion of said bore, each of said gaskets having a soft metallieshell and' an asbestos core;v

saidl gaskets operatingthrough their friotionalengagement with said insulator and v body to hold' the insulator inthe body.

- ln a spark plug, e bodyhaving 'a bore formed therein and provided. with a seat gradually' tapered toward one end of the body,.an insulator positioned in said body and having a1 surface tapered inthe same direction as said seat and having-a shoulder'bee low said surface, ay plurality of gaskets encircling the tapered part of said insulator and operating through their rictiona'l engagement with said insulator and said body to hold the insulator' in the body; and a i in saidbore and having' a part tapered in the same direction as said.

metal sleeve fast said bore immediately' below said shoulder.

6. ln a spark plug, a body having a bore formed therethrough, said bore having .a

portion gradually tapered toward the outer end oi' the. body, 'en insulator positioned in l said bore and having a part tapered to correspond to the taper of said bore and having an enlarged portion below said taper, a plurality oi gaskets independent of each other encircling the 'tapered part of said insulator and tilling the space above said enlargement between the tapered surface of the insulator and the tapered bore of the body, said gasket serving to maintain the insulator in thev body through their Afrio- .FREDERICK M. FURBER.

et patent may be ebtnnel fer eve cents each, by addressing the hnmmilsioner of listenin,

Washington, D. G. 

